In the third Fitt, there is an "exchange game." What do you think of Gawain's performance with Bercilaks wife?
In Sir Gawain and the Green Knight, Gawain fails the test by not sharing the magic girdle or belt with the Green Knight (the owner of the castle who goes unrecognized). This results later in the scratch that the Green Knight gives Gawain on his third strike at Gawain's neck. Gawain has failed to uphold the strict chivalric code of honor.
Gawain passes the test put to him by the Green Knight's wife, though. She repeatedly tries to seduce him, but he politely declines. This is why the Green Knight purposely does not scratch Gawain on his first two strikes with his blade.
Those are the details, but I can't really help you with what you think of them. I personally don't have an opinion: the story is what it is and it reflects the conventions of medieval romance literature.
Importantly, though, the fact that Gawain fails at all is of importance. This is a small but important step toward creating characters in literature that are more realistic and human-like that is credited to Sir Gawain and the Green Knight.
In the book "Sir Gawain and the Green Knight" Gawain goes in search of the Green Knight. He stays with a family on the way. The man offers that Sir Gawain stay back at the house and he will do the hunting. He says he will give Sir Gawain whatever he catches if Sir Gawain gives to him whatever he gets.
Day 1 the man's wife tries to seduce Gawain. He refuses and she gives him one kiss. He gives it to the man.
Day 2 the same things happen and he gets two kisses. He gives them to the man.
Day 3 the same thing happens and he gives the man the three kisses but keeps the green girdle that is supposedly able to protect him.
Under the odd circumstances Sir Gawain has been correct in his behavior. He did not accept the man's wife's seductions. However, he did give the man what he had received.